HPP Enterprises P4000 SAN - Manual (Page 48)

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Figure 41. Backing up the VM metadata
VM metadata backup data is stored on a special backup disk in this SR. The backup creates a new
virtual disk image containing the resource pool database, SR metadata, VM metadata, and template
metadata. This VDI is stored on the selected SR and is listed with the name Pool Metadata Backup.
You can create a schedule (Daily, Weekly, or Monthly) to perform this backup automatically.
The xsconsole command can also be used to restore VM metadata from the selected source SR. This
command only restores the metadata; physical SRs and their associated data must be backed up from
the storage.
SAN based Snapshots
Storage based snapshots provide storage consistent points of recovery. Initiated from the HP
StorageWorks Centralized Management Controller or storage CLI, iSCSI volumes may create
consistency checkpoints from which the volume may be rolled back to that point in time. The
advantage of creating snapshots from the storage perspective is that very efficient features exist for
working with these views of data. A snapshot can be thought of like any other volume in a point in
time. The snapshot retains space efficiency, in the case of thinly provisioned snapshots, by only
utilizing delta changes from writes to the original volume. In addition, snapshots and multiple levels of
snapshots do not affect XenServer host efficiency to the original iSCSI volume, unlike snapshots
originating from within XenServer Hosts on LVM over iSCSI volumes. Also, snapshots may be
scheduled with retention schedules, for local clusters or even sent to remote locations with storage
based efficiency of resource utilization. Remote snapshots have an added advantage of only pushing
small deltas maximizing bandwidth availability. Remote Snapshots are discussed as the primary
approach of Multi-Site Asynchronous SAN configurations.
Due to XenServer Host requirements on unique UUIDs at the storage repository and virtual disk level,
the primary use of snapshots will be left to: disaster recoverability at remote sites from unique
resource pools, consistency recoverability points for rolling back a volume to a point in time, and the
source for creating new volume. Snapshots created from the HP StorageWorks P4000 SANs are
read only consistency points that support a temporary writeable space to be mounted. This temporary
white space does not persist a SAN reboot and may also be cleared manually. Since a duplicate
Storage Repository must contain unique UUID SR and virtual disk data, it is impractical to manually go